The present invention relates to a slide gate nozzle or sliding closure unit for controlling the discharge of molten material from a vessel, such unit being of the type including stationary and sliding refractory valve bodies, such as plate shaped members, supported in respective support frames with lateral play or clearance between each refractory valve body and the respective support frame, and the refractory valve bodies having complementary abutting relative sliding surfaces.
The present invention furthermore relates to a refractory valve body usable as a stationary or sliding valve member in such slide gate nozzle or sliding closure unit.
A sliding closure unit of the above type is disclosed in DE-A1 28 21 839, wherein a refractory valve body inserted in a support frame with lateral play is tightened and centered by at least one eccentric which is removably held to the support frame and the eccentric surface of which acts on a metal jacket surrounding the refractory valve body. The valve body is tightened in the support frame by means of a rotary tool operating on the eccentric. This arrangement however produces pressure and binding stresses on the refractory valve body, especially when it is in a heated condition during use. This leads to the substantial disadvantage of cracking of the valve body and thus to reduced service life thereof. Since the valve bodies generally are manufactured with rather large tolerances relating to circumferential or peripheral dimensions, it often will occur that valve bodies are formed with dimensions near the lower limit of such tolerance. When this occurs, the eccentrics will not be able to exert tension on the valve bodies when mounting them in the support frames. A further disadvantage of this arrangement is the fact that it is not possible to precisely center the valve bodies with respect to the support frames.
Another sliding closure unit of this general type is disclosed in EP-A1 0 040 340, wherein refractory valve bodies are clamped between two support frame parts by means of screws or bolts. Holes or slots are provided in the frame parts to enable the insertion of dowels attached to the support frame. The valve bodies are in the form of generally rectangular plates and are held at all corners thereof by the dowels. A disadvantage of this arrangement is the fact that the refractory plates, which expand substantially during operation as a result of being heated, also are exposed to additional pressure and binding stresses, thereby provided a negative effect on the service life of the refractory plates. In addition, the refractory plates must be manufactured with precise tolerances on the lateral sides thereof so that they can be properly inserted together with the frame parts into the respective support frame.